On account of many superior properties, room temperature curable organopolysiloxane compositions are used in a wide range of application including civil engineering, building, general industry, and electrical and electronic fields. However, most room temperature curable organopolysiloxane compositions suffer from poor self-extinguishing properties. Attempts have been made to improve the self-extinguishing properties of such compositions by adding and compounding large amounts of extending fillers such as crystalline silica, zinc carbonate, aluminum hydroxide and carbon black, and by adding and compounding platinum or platinum compounds. In either attempt, the self-extinguishing properties achieved thereby are still short. Additionally, these compositions become less effectively workable, and especially have the crucial drawback of difficult extrusion from a container.
To overcome the above-mentioned drawbacks, JP-A 54-90349 proposes a room temperature curable polyorganosiloxane composition loaded with aluminum hydroxide treated with stearic acid or metaphosphoric acid. Similarly, JP-A 4-198365 and JP-A 5-12528 disclose room temperature curable organosiloxane compositions loaded with a mixture of aluminum hydroxide and calcium carbonate. These compositions are still unsatisfactory in shelf stability, workability, and retention of self-extinguishing properties.